Expression of WT1 in Salivary Gland Neoplasms

Claire Andrews, Cellular Pathology

Claire Andrews and Gerald Langman

Ancillary techniques, including immunohistochemistry, are of limited use in the diagnosis, classification and prognostication of salivary gland neoplasms. Wilm€™s Tumour 1 (WT-1) protein is overexpressed in a variety of tumours. Originally diagnosed in Wilms tumour, immunohistochemistry is valuable in the diagnostic workup of mesotheliomas and serous tumours of the ovary. Previous studies have demonstrated the upregulation of WT-1 mRNA in epithelial derived salivary gland neoplasms. The aim of this study was to investigate the use of WT-1 immunohistochemistry as a diagnostic tool in salivary gland neoplasms. Samples of pleomorphic adenoma (15), Warthin€™s tumour (15), adenoid cystic carcinoma (15), mucoepidermoid (6), acinic cell carcinoma (9), epithelial-myoepithelial carcinoma (1) and normal salivary gland tissue (15) were stained with the WT-1 protein antibody using the Ventana Benchmark XT and the Ultraview detection system. Further staining with p63, calponin and smooth muscle actin (SMA) was performed in selected cases. Myoepithelial cells in pleomorphic adenomas and epithelial-myoepithelial carcinoma showed positive cytoplasmic staining for WT-1. Adenoid cystic carcinomas showed paranuclear dot-like staining in poorly differentiated areas with a solid growth pattern. All the other tumours as well as the normal tissue showed no WT-1 expression. The results suggest that WT-1 is a marker of salivary gland myoepithelial cells. Unlike the other known myoepithelial markers, is does not stain the non-neoplastic cells. WT-1 may also have a role in the diagnosis of poorly differentiated adenoid cystic carcinomas.